Surgical device for the temporary protection of anastomosis

ABSTRACT

A surgical device ( 1 ) for temporary protection of an anastomosis ( 5 ) in the colon ( 12, 13, 14 ), the rectum ( 11 ), or the anal passage ( 10 ), including: a) a semi-rigid hollow longitudinal temporary anchor element ( 2 ), a first wall of which includes a substantially cylindrical main portion ( 2   a ) with a substantially circular section having a length (L 1 ) of at least 50 mm, preferably in the range 70 mm to 150 mm, said first wall having an outside diameter that may be varied in a controlled manner; and b) a flexible sheath ( 3 ) fixed to said anchor element ( 2 ) against, preferably around, said first wall and having a length (L 3 ) downstream of said anchor element ( 2 ) of at least 50 cm, preferably at least 1 m, and an outside diameter when at rest in the range 20 mm to 40 mm, preferably in the range 25 mm to 33 mm, and said sheath is made from a biocompatible elastomer material having a wall thickness in the range 0.05 mm to 1 mm.

This application is a 371 of PCT/FR2010/050210 filed on Feb. 9, 2010,which is incorporated herein by reference.

The present invention relates to a surgical device for the temporaryprotection of an anastomosis in the colon, rectum or anal passage.

The subject matter of the invention is thus a device for protecting ananastomosis (join) produced between the two ends of an intestinalsegment to prevent or reduce the risk of separation known as anastomoticfistula. The resulting leaks may cause infections, abscesses, orperitonitis, all major causes of post-operative complications andmortality.

The technique used at present entails diverting the intestinal flowupstream of the anastomosis area. A segment of the intestine situatedupstream of the anastomosis is brought out via the abdominal wall. Thisis known as a digestive stoma. The fecal bolus is then collected outsidethe abdomen, in a bag stuck to the abdominal wall around the intestine,also known as a pouch. This technique makes it possible to divert thefecal bolus upstream of the anastomosis, but at the cost of a stoma. Astoma has considerable socio-professional repercussions, however, and asignificant level of local (cutaneous and intestinal) and general(dehydration) complications. Moreover, closing the stoma six to eightweeks later requires a new surgical intervention with a non-negligiblemortality rate. Finally, the pouch and care of the stoma are costly.

A known alternative to a stoma is referred to as a bypass. With thattechnique there is no digestive diversion. The anastomosis area isprotected from fecal contact by an interface. The interface is a veryflexible (for example vinyl) tube that is introduced into the lumen ofthe intestine and attached to the proximal end thereof by a resorbablesuture upstream of the area of the future anastomosis. The other end ofthe tube is free within the lumen of the distal intestine. Theanastomosis is then produced. After an average delay of ten daysnecessary for proper healing of the anastomosis, and once the fixingsutures have been resorbed, the tube is spontaneously eliminated peranum with the fecal bolus.

That method was first described many years ago and the COLOSHIELD®system has been commercially available since 1992. Experimental andclinical work has confirmed the reliability of this system. However,that product has not been used by surgical teams for many years becauseit has several drawbacks.

One drawback of the COLOSHIELD® system is its attachment to the lumen ofthe intestine upstream of the future anastomosis area. That requireseversion of the proximal end of the intestine in order to expose itsinternal face and to fix the tube thereto by resorbable sutures. Thismaneuver is the source of traction on, injury to, or tearing of theintestine at the very place where it must be joined to the distal end ofthe intestine. Another drawback of that system is the impossibility ofusing an automatic circular stapler to produce the anastomosis. Morethan 80% of colorectal anastomoses are produced using such machines.

WO 03/094785 discloses a conical or funnel-shaped permanent anchorelement made from a plastics material provided with a valve implantedpermanently at the start of the digestive tube, notably in the smallintestine, and coupled to a flexible sheath extending into the smallintestine downstream of said anchor element, that system being intendedto treat obesity. Said anchor element has an outside diameter slightlygreater than that of the intestine, even in its dilated phase duringintestinal transit, because said anchor element must remain fixed to thestomach permanently by sutures.

US 2008/0208357 discloses a method of the curative treatment offistulas, i.e. leaking of the contents of the intestine at agastro-intestinal anastomosis, the method including the use of an anchorelement consisting of a stent 25 millimeters (mm) to 45 mm long and 20mm to 40 mm in diameter coupled to a short flexible sheath for repairingand blocking the fistula or leak. That stent is introduced into theesophagus via the mouth and installed above the area of reducedanatomical section at the junction between the esophagus and thestomach. The stent installed in the oesophageous in this manner must notmigrate and in any event is prevented from migrating by virtue of itsinstallation upstream of the area of reduced anatomical section at thejunction between the esophagus and the stomach.

In US 2008/0208357 the length of the sheath is necessarily less than thelength of the jejunal loop that is anastomosed to the stomach(approximately 60 centimeters (cm)). The device must necessarily beintroduced via the mouth, as mentioned above. Once the stent is inplace, the sheath must be pushed downstream of the stent so as to bedeployed in the jejunal loop. The total distance between the oral cavityand the distal end of the deployed sheath is in the range 57 cm to 72cm. In practice, it would not be possible to deploy a sheath longer than15 cm to 30 cm by pushing it in this way. Moreover, that maneuver ofpushing in the sheath is hazardous for the anastomosis because it iseffected in an area that is greatly weakened by the fistula and mayaggravate the state of the fistula.

Finally, in US 2008/0208357 the sheath is very thin (in the range 0.01mm to 0.025 mm thick), because in this application the sheath must notirritate the esophagus, which is particularly sensitive. However,because it is so thin, that kind of sheath cannot have shape memory. Itmay be subject to plication or twisting. That is why the above patentrefers to another patent, U.S. Pat. No. 7,267,794, relating to the useof a device in the form of a circular metal wire that prevents twistingof the sheath.

The problem addressed by the present invention is to provide a devicefor temporary protection of an anastomosis of the bypass type in thecolon, which device is inserted after producing the anastomosis andregardless of the technique used (suture or stapler), it requires nofixing maneuvers, and it is eliminated spontaneously without surgicalintervention after a sufficient delay following healing of theanastomosis.

To this end, the present invention provides a surgical device fortemporary protection of an anastomosis in the colon, rectum, or analpassage, the device including:

a) a semi-rigid hollow longitudinal element called temporary anchorelement, a first wall of which defines a surface of revolution about alongitudinal axis XX, including a substantially cylindrical main portionwith a substantially circular section, and said first wall having anoutside diameter that may be varied in a controlled manner between:

-   -   a reduced outside diameter D1′ of at most 10 mm in a radially        retracted configuration of said first wall; and    -   a maximum outside diameter D1 in a maximum radial expansion        configuration of the main portion of said first wall in the        range 20 mm to 40 mm, preferably in the range 25 mm to 33 mm;        and

b) a sheath having a flexible tubular wall fixed against, preferablyaround, said first wall of said anchor element (2);

which device is characterized in that:

1) said first wall of said temporary anchor element includes a said mainportion of greater diameter having a length L1 of at least 50 mm,preferably in the range 70 mm to 150 mm; and

2) said sheath has when at rest a length L3 downstream of said anchorelement of at least 50 cm, preferably at least 1 meter (m), and anoutside diameter in the range 20 mm to 40 mm, preferably in the range 25mm to 33 mm, and is made from a biocompatible elastomer material havinga wall thickness in the range 0.05 mm to 1 mm.

The reduced outside diameter D′₁ in the radially retracted configurationof said first wall makes it possible to introduce said anchor element inthis radially retracted configuration per anum and then to route it inthe colon as far as a temporary anchor position upstream of ananastomosis in the colon, rectum, or anal passage, and the maximumoutside diameter D₁ in the maximum radially expanded configuration ofsaid wall makes it possible for said anchor element, in the absence ofintestinal transit, to remain temporarily anchored by the radialexpansion force against the intestinal wall and to be released and beginto migrate when the intestine contracts and expands during what iscalled the peristaltism phase on resumption of intestinal transit.

With reference to said anchor element:

-   -   the expression “semi-rigid” means that in each of the retracted        and expanded configurations said first wall of said anchor        element retains a given shape defining a said surface of        revolution; and    -   the expression “outside diameter that may be varied in a        controlled manner” means that the diameter of said first wall        may vary in a manner determined as a function of conditions of        use of the device, regardless of parameters such as temperature,        and/or independent mechanical means cooperating with said anchor        elements such as a fitting instrument, notably an introducer        sheath, as explained below.

It is clear that said anchor element may adopt:

-   -   a reduced outside diameter D′₁ of said first wall at least less        than that of the intestine when at rest, preferably less than 10        mm, so that it may be introduced per anum as far as the upstream        side of an anastomosis in the intestine; and    -   an outside diameter D₁ in the maximum radially expanded        configuration of said first wall greater than or equal to that        of the intestine when at rest so that it may be temporarily        anchored by virtue of bearing on the intestinal wall by radial        expansion at least over a part of said anchor element, the        diameter D₁ always remaining less than the maximum diameter of        the intestine in the peristaltism phase so that said anchor        element remains fixed against the wall of the intestine in the        absence of intestinal transit, notably during the post-operative        paralytic ileus phase of intestinal paralysis, but is no longer        fixed to the intestine and in practice upon resumption of        intestinal transit begins to migrate by sliding along the        intestinal wall.

A standard way to determine the diameter D₁ is to calibrate the sectionof one of the ends of the intestine by means of instruments known asbougies, which are routinely used by surgeons. Another way to determinethe diameter D₁ is, where applicable, to consider it equal to thediameter of the stapler used to produce the mechanical anastomosis. Thediameter D₁ may then more particularly vary in the range 25 mm to 33 mm,corresponding to the outside diameter of staplers commercially availableat present.

The expression “longitudinal end” means an end of said anchor element orwhere applicable said sheath in the longitudinal direction.

References to the length and diameter of the sheath “when at rest” meanits length and diameter respectively when its longitudinal and radialelasticity are not loaded.

After resumption of intestinal transit, peristalsis of the intestineresults in release of said anchor element and migration of the releasedanchor element, but the radial expansion properties of the anchorelement enable its external wall to continue to slide in contact withthe internal wall of the intestine and thus to produce a sufficient sealand therefore to continue to protect the anastomosis by preventing thefecal bolus passing between the outside wall of the anchor element andthe inside wall of the intestine. The fecal bolus must travel throughthe sheath and remains well separated from the intestinal wall at thelevel of the anastomosis.

The above values of the radially expanded diameter of the anchor elementare slightly greater than the diameter of the intestine when at rest,varying according to the patient but less than the maximum diameter ofthe intestine when dilated during intestinal transit, which is in therange 30 mm to 60 mm. Moreover, the length of said main portion is suchthat the area of contact between said anchor element and the wall of thecolon combined with the radial expansion force are such that said anchorelement in the maximum expansion configuration remains temporarily fixedby virtue of its radial expansion force against the wall of theintestine upstream of the anastomosis and does not migrate in theabsence of intestinal transit for at least three days, preferably fivedays, after it is anchored. Without a length of at least 50 mm of themain portion in contact with the colon, said anchor element could notremain anchored for at least three days without using fixing means,thereafter requiring means and/or interventions to deactivate the fixingmeans and enable its migration, or without using anchor elements havinga larger maximum expansion diameter, which could injure the colon andbesides could prevent natural release of the anchor element onresumption of transit.

In contrast, the length of the sheath is such that the distance betweenthe anastomosis and the upstream anchor site may be at least 50 cm,preferably at least 1 m, and said anchor element may be anchored in thecolon sufficiently upstream of the anastomosis for its migration timebetween said anchor position and said anastomosis on resumption oftransit to be at least three days, preferably at least six days, and forsaid sheath to protect the anastomosis, or even to project per anum whensaid anchor element is in the anchor position.

Accordingly, given that the post-operative intestinal paralysis phaseknown as paralytic ileus lasts three to five days, it is possible toprotect the anastomosis in this way for the same period plus the timethat said anchor element takes once released to migrate between itsanchor site upstream of the anastomosis and the site of the anastomosis,this migration time depending on the distance to be travelled betweenthe anchor site and the anastomosis. In practice, a distance of 50 cm to1 m is reflected in a migration time of three to six days, so that intotal the anastomosis is protected for at least six to eleven days afterit is produced.

Clearly, because it consists of an elastomer, said sheath has radial andlongitudinal stretch properties similar to those of the intestinal wall,which properties are those of an elastomer material (the sheath) havingradial and longitudinal elasticity properties. These radial andlongitudinal elasticity properties of the sheath are similar to those ofthe wall of the colon and enable intestinal transit to be effectedcorrectly in said sheath throughout the period of migration of theanchor element, that is to say at least six to ten days.

The longitudinal elasticity of the elastomer sheath may be greater thanthat of the intestine without causing problems, and to the contrary hasthe advantage that the sheath portion projecting per anum may be pulledon, in order to cut it, and then retract in the upstream direction,inside the rectum.

By virtue of its radial elasticity, said longitudinal end of the sheathremains fixed to said end of said anchor element whatever its radialexpansion.

Moreover, the thickness characteristics of the sheath combined with itselasticity give it shape memory properties. Here the expression “shapememory properties” refers to the fact that the elastomer material ofsaid sheath naturally returns to its initial shape after it is deformedby bending. Given the great length of the sheath, the shape memoryproperties are important for the material to resume its longitudinalshape naturally without blocking transit in the event of plication ofthe sheath, which may occur during its migration after releasing theanchor element.

In a preferred embodiment said main portion of said first wall extendsfrom the upstream longitudinal end of said first wall as far as anappropriately shaped downstream end portion having a smaller diameterthan the cylindrical main portion, the outside diameter D2 of thedownstream end of said first wall in the maximum radial expansionconfiguration being in the range 20 mm to 35 mm and the length L2 ofsaid appropriately shaped end portion of the first wall being in therange 10 mm to 30 mm, preferably in the range 15 mm to 25 mm, thediameter of said end portion preferably decreasing progressively betweensaid main portion and said downstream end of said first wall.

To prevent jamming at this level, the appropriately shaped downstreamportion of the anchor element facilitates its migration through theanastomosis area, which generally has a reduced passage diametercompared to the colon upstream and downstream of the anastomosis area.This reduced diameter is the result of a stenosis at the level of theanastomosis. In contrast, an appropriately shaped upstream portion ofthe anchor element would lead to the risk of leakage between the anchorelement and the intestinal wall.

More particularly, the diameter of said appropriately shaped downstreamend portion is reduced by surrounding it with an elastomer material ringhaving a diameter less than said diameter of said main portion in saidmaximum radial expansion configuration.

Preferably:

-   -   said anchor element is made from a material conferring on it        radial elasticity properties such that it may be compressed        radially in said retracted configuration and adopt said maximum        radial expansion configuration after the radial compression is        released; and    -   said sheath is made from an elastomer-based biocompatible        polymer material of the silicone or polyurethane type having a        wall thickness in the range 0.1 mm to 0.5 mm and having radial        and longitudinal elasticity properties, shape memory properties,        and non-stick properties.

The expression “non-stick properties” refers to the fact that theelastomer material of said sheath has a coefficient of adhesion suchthat the two opposite surfaces of the inside wall of the sheath do notstick together on folding and therefore do not create any resistance tothe passage of gas and material.

Said anchor element may be held in the radially retracted configurationwith an instrument known as an introducer sheath described below, radialexpansion occurring after disengagement of the anchor element from theintroducer sheath.

It is also clear that:

-   -   said sheath has a diameter when at rest substantially as least        equal to said reduced outside diameter D′₁ of said hollow anchor        element when radially retracted and less than that of the        intestine when at rest, and said diameter of said sheath when at        rest is preferably substantially equal to that of the intestinal        wall when at rest; and    -   said sheath extends downstream of the end of said anchor element        to which it is fixed over a length corresponding to the distance        between the anchor position upstream of said anastomosis and a        downstream position, preferably as far as the anal orifice.

More particularly, the thickness of said first wall of the anchorelement is in the range 0.5 mm to 5 mm, preferably in the range 1 mm to3 mm.

The longitudinal elasticity of the elastomer sheath may be greater thanthat of the intestine without causing any problems, and to the contraryhas the advantage that if necessary it is possible to pull on theportion of the sheath protruding from the anus, so as to be able to cutit, and that it then retracts inside the rectum or the anal passage.

Said first wall of said anchor element may be solid or perforated,notably by pores or miniperforations.

In one particular embodiment, said hollow longitudinal temporary anchorelement is a stent-type enteral prosthesis the tubular wall of which iscovered on at least its outside surface with a biocompatible syntheticmaterial coating, preferably a silicone or polyurethane type elastomer.

This external coating is doubly advantageous in that it facilitatesdeployment of said anchor element by sliding it along the intestinalwall on resumption of transit and in that during anchorage it protectsthe intestinal wall against which said longitudinal element is expanded;this element could otherwise become incorporated into the tissue of theintestinal wall and prevent subsequent re-release, or even perforate theintestinal wall.

These stent type enteral prostheses have been used on intestinal tumorsfor some twenty years, mainly in the palliative treatment of tumoralstenosis (shrinkage) of the esophagus, duodenum, or colon. They were notdesigned for temporarily anchoring a device for protecting an intestinalanastomosis in the manner of the present invention. In other words,there has never been proposed an enteral prosthesis attached to aflexible sleeve, the assembly being designed with the dimensionalcharacteristics and notably the elasticity characteristics defined aboveto protect a digestive anastomosis.

The temporary anchor element is preferably an enteral prosthesis thefirst wall of which is formed by a spiral mesh of metal or elastomermaterial filaments, notably filaments of an elastomer material based onsilicone, preferably coated with a layer of biocompatible syntheticmaterial that covers said mesh, said coating preferably being abiocompatible elastomer material such as silicone.

As is known in the art, radial expansion is then the result of the metalwires crossing at an angle that varies, thus varying the width of thelozenge or parallelogram shape of the meshes of said spiral wire mesh.

The anchor element is advantageously made from a material that conferson it expansion by radial elasticity properties only at a temperature atleast equal to an ambient temperature of 20° C., notably at thetemperature of the human body, said anchor element being in saidradially retracted configuration at a temperature below said ambienttemperature, preferably below 5° C. Clearly the tubular material changesdiameter automatically as a function of ambient temperature.

Even more particularly, said anchor element is an enteral prosthesissaid first wall of which is formed by a spiral wire, preferably nitinolwire, mesh.

Nitinol is a metal alloy having properties of progressive radialexpansion as a function of temperature at a temperature greater than orequal to ambient temperature (25° C.), enabling it to retain itsretracted shape at lower temperatures, notably in storage at 4° C. Onceretracted at low temperature, it remains retracted in this way for longenough to be able to place it in the introducer sheath and to route itin the intestine using said introducer sheath. Once released inside theintestine, the prosthesis progressively expands in the radial directionbecause of the effect of a higher ambient temperature, namely that ofthe human body.

In one particular embodiment, the connection between said sheath and theanchor element is such that the end of said sheath adheres to andelastically covers at least the surface of the longitudinal end of saidhollow longitudinal element.

In a preferred variant, said sheath adheres to and elastically coversthe outside surface of said anchor element at least over the outsidesurface of the downstream end of said anchor element. Said sheath thushas a coating function and where applicable covers the mesh of theanchor element.

The above two embodiments may use for the fabrication of the sheath amethod of dipping a solid molding tube, where appropriate in line withan anchor element, into a bath of said polymer composition, onto whichtube said polymer material is molded, said hollow longitudinal elementbeing threaded onto said solid molding tube before dipping.

To provide the radial expansion properties of the elastomer sheath,given the thickness employed (in the range 0.05 mm to 0.4 mm), it isnecessary to use elastomer compositions having some hardness, as well asstickability (adhesion coefficient), and shape memory (DRC, degree ofremanent compression), the selected value ranges of which are explainedbelow.

More particularly, said sheath is made from an elastomer-basedbiocompatible polymer material, preferably of the silicone and/orpolyurethane type, having the following properties:

-   -   a Shore A hardness in the range 5 to 95, preferably in the range        50 to 70;    -   a degree of remanent deformation on compression (RDC) in the        range 10% to 35%, preferably in the range 17% to 23%; and    -   a coefficient of friction in the range 0.30 to 0.90, preferably        in the range 0.35 to 0.45.

The term “hardness” refers to the energy of elastic deformation of anelastomer, here expressed as a Shore A hardness, for example, inaccordance with the DIN 53505 standard.

The expression “degree of remanent compression” (DRC) refers to thedegree of residual deformation after releasing a load on an elastomersample after a particular time, according to the test specified in theDIN 53517 ISO 815B standard, for example the shape memory property onbending, the material reverting to an unbent shape as soon as thecompression that caused it to bend is released.

The coefficient of friction may be measured according to the ASTM D1894standard, for example.

The above values of the coefficient of friction prevent adhesion betweentwo opposite faces of the internal wall of the sheath when in contacteach other, firstly so as not to create any resistance to the passage ofgases and materials in the sheath and secondly so that if it is bent,the sheath is not blocked by closing on itself.

Even more particularly, said sheath is made from a biocompatible polymermaterial based on silicone including at least the following compounds:

-   -   75 wt % to 95 wt % of a liquid silicone rubber (LSR) grade or        quality elastomer;    -   2.5 wt % to 12.5 wt % of an RTV grade or quality elastomer; and    -   2.5 wt % to 12.5 wt % of a gel grade or quality elastomer.

This combination of elastomers of different grades (LSR, RTV, gel) isadvantageous because:

-   -   an LSR grade or quality elastomer contributes resistance to        tearing;    -   an RTV grade or quality elastomer contributes radial and        longitudinal elasticity properties; and    -   a gel grade or quality elastomer contributes a reduced        coefficient of adhesion (non-stick property).

In a preferred embodiment, said anchor element is a stent-type enteralprosthesis covered on at least its outside surface with a coating ofsilicone or polyurethane type elastomer synthetic material, saidelastomer coating being more flexible than the elastomer material ofsaid sheath, the connection between said sheath and said anchor elementbeing effected by said sheath covering said anchor element over onlypart of the length of said anchor element including at least itsappropriately shaped downstream end of progressively reducing diameter.

Stent-type enteral prostheses of this type coated with elastomer,notably a silicone-based elastomer, are well known in the art andcommercially available. Thus the elastomer coating of the stent hasgreater radial and longitudinal deformability than the elastomer of thesheath, i.e. the elastomer coating of the stent consists whereappropriate of a mixture of different types of RTV grade silicone havinga weight percentage greater than that of the elastomer of the sheath butstill within the 2.5 wt % to 12.5 wt % range referred to above.

As explained below, by applying traction to the sheath, this embodimentmakes it possible to induce a diameter reduction and axial elongation ofthe stent enabling it to be detached from the intestine to facilitateits migration through the anastomosis on release of said anchor element.

A stent type anchor element is advantageously used that includes at itsends an elongate or thread-like extension known in the art as a lasso,making it possible, in a manner known to the person skilled in the art,and where applicable using a tool such as a colonoscope, to applytraction to the end of said stent type anchor element in order tofacilitate its release and/or its migration via the anastomosis areawhen this is required, in order to prevent it jamming at this level.

Said polymer material of said sheath advantageously includesradio-opaque, notably barium sulfate, filaments disposed in thelongitudinal direction of the tube.

These filaments make it possible to track the migration of the sheathand to monitor its initial positioning and thereafter its progressivemigration during its elimination. Moreover, the longitudinal dispositionof these filaments confers simultaneously on the sheath resistance toelongation and reduced longitudinal elasticity, which otherwise might beexcessive, for example compared to that of the intestine (see above).

The sheath is advantageously graduated in the increasing directionstarting from its upstream end.

More particularly, the introducer sheath may in known manner consist ofa semi-rigid guide tube of the catheter type provided at one of its endswith a handle and the inside diameter and the length of which enableaccommodation therein of said anchor element in its retracted form andsaid sheath, preferably deployed longitudinally.

Nevertheless, said device preferably further includes an introducersheath including:

-   -   a tubular external envelope that is adapted to contain said        anchor element when compressed in said retracted configuration        and to retain it inside the distal end of said external envelope        and is sufficiently long also to contain said sheath, said        external envelope preferably having a length of at least 110 cm,        preferably at least 150 cm; and    -   means for routing the distal end of said introducer sheath from        the anal orifice to said anchor site in the intestine upstream        of the anastomosis; and    -   preferably, means for disengaging said anchor element from the        external envelope, preferably in the form of a buffer tube        including an abutment at its distal end, where appropriate in        contact with the longitudinal end of said anchor element, said        sheath downstream of the anchor element surrounding said buffer        tube inside said external envelope.

The shrinkage of the external envelope and then of the buffer tubeenable complete deployment of the sheath downstream of the anchorelement without any additional maneuver by the surgeon being necessaryto deploy the sheath.

The device of the invention preferably further includes a protectortube, preferably a protector tube having an outside diameter in therange 20 mm to 40 mm and a length in the range 10 mm to 25 cm, thatincludes a portion of curved shape conforming to the curvature of thesacral concavity, is stiffer than the external envelope of theintroducer sheath, has an outside diameter and length such that saidprotector tube may be introduced via the anal orifice and extend betweenthe anal orifice and a point upstream of said anastomosis, and has aninside diameter and a curvature conforming to the curvature of thesacral concavity such that said protector tube is able to contain saidintroducer sheath and route it between the anal orifice and saidanastomosis.

The present invention enables the use of a surgical treatment methodemploying a surgical device of the invention to provide temporaryprotection of an anastomosis in the large intestine or colon, therectum, or the anal passage, in order to prevent or reduce the risk ofanastomotic fistula, by effecting the following successive steps:

1) Said surgical device is introduced per anum and routed as far as ananchor site upstream of the anastomosis area, the anchor element beingretained in said radially retracted configuration with diameter D′₁ androuted using an instrument known as an introducer sheath and the lengthof said elastomer sheath being at least equal to the distance betweenthe anchor site and the anal orifice.

2) The introducer sheath is disengaged from said anchor element once ithas been routed to said anchor site to enable said anchor element toadopt an anchor position against the intestinal wall in said maximumradially expanded configuration.

The distance between said anchor position and said anastomosis ispreferably at least equal to the distance travelled by said anchorelement in at least three days, preferably at least five days, whenmigrating once released from said intestinal wall and by the resumptionof intestinal transit.

More particularly, the distance between the anastomosis and the anchorsite is at least 50 cm, preferably at least 1 m.

Even more particularly, in the absence of resumption of intestinaltransit said anchor element remains anchored in said anchor position forat least three days, preferably at least five days, after it isanchored.

Accordingly, given that the post-operative intestinal paralysis phaseknown as paralytic ileus lasts from three to five days, it is possiblein this way to protect the anastomosis for the same period, plus thetime that said anchor element takes to migrate after it is releasedbetween its anchor site upstream of the anastomosis and the site of theanastomosis, given that this migration time depends on the distance tobe travelled between the anchor site and the anastomosis. In practice adistance of 50 cm to 1 m is reflected in a migration time of three tosix days, so that in total the anastomosis is protected for six toeleven days after it is produced.

Said introducer sheath is preferably introduced by pushing it inside asemi-rigid protector tube, the protector tube preferably having outsidediameter in the range 20 mm to 40 mm and a length in the range 10 mm to25 cm, which includes a part of curved shape conforming to the curvatureof the sacral concavity, is of greater stiffness than the externalenvelope of the introducer sheath, has outside diameter and length suchthat said protector tube can be introduced via the anal orifice andextend between the anal orifice and as far as a point upstream of saidanastomosis, and has an inside diameter and a curvature, conforming tothe curvature of the sacral concavity, such that the protector tube isable to contain said introducer sheath and to enable it to be routedbetween the anal orifice and said anastomosis, the latter tube extendingbetween the anal orifice and said anastomosis.

Once released from said intestinal wall, the migrating anchor element ispreferably recovered by a resumption of intestinal transit in aprotector tube, preferably taking the form of a tube having an outsidediameter in the range 20 mm to 40 mm and a length in the range 10 cm to25 cm, that has a semi-rigid curved part conforming to the curvature ofthe sacral concavity, is of greater stiffness than the external envelopeof the introducer sheath, has an outside diameter and length such thatsaid protector tube may be introduced via the anal orifice and extendbetween the anal orifice and a point upstream of said anastomosis, andhas an inside diameter and a curvature, conforming to the curvature ofthe sacral concavity, such that the protector tube is able to containsaid introducer sheath and to enable it to be routed between the analorifice and said anastomosis, the protector tube extending between theanal orifice and said anastomosis.

Other features and advantages of the present invention become apparentin the light of the following detailed description given with referenceto FIGS. 1 to 11, in which:

FIG. 1 represents diagrammatically a device of the invention;

FIG. 2 is a view in longitudinal section of a device of one embodimentof the invention with a downstream end portion 2 b of an appropriatelyshaped anchor element having a reduced diameter compared to acylindrical main portion;

FIG. 3 is a diagrammatic view of the digestive system, with ananastomosis 5;

FIG. 4 is a diagrammatic view of the device of the invention routed toits implantation site via an introducer sheath 4, the anchor element 2being in its retracted radial configuration on leaving the introducersheath and the sheath 3 still being housed inside the introducer sheath;

FIG. 5 represents part of the device of the invention in the anchorposition, the anchor element being retained in the maximum radiallyexpanded configuration and immobilized against the intestinal wall;

FIG. 6 represents diagrammatically the device of the present inventionin an anchor position in which the anastomosis is protected, the sheath3 being deployed downstream of the anchor element 2;

FIGS. 7A and 7B represent the device of the invention when migratingduring the elimination peristalsis phase (FIG. 7A) and at the end ofelimination (FIG. 7B);

FIG. 8 represents an introducer sheath of the invention;

FIG. 9 represents a protector tube of the invention;

FIG. 10 represents an introducer sheath of the invention passed throughthe protector tube at the level of the sacral concavity; and

FIG. 11 is a diagrammatic view of a device of a preferred embodiment ofthe invention.

FIG. 1 shows a surgical device of the invention including:

-   -   an anchor element 2 consisting of an enteral prosthesis of the        type described below in a maximum radially expanded        configuration; and    -   a flexible silicone sheath 3 attached to the downstream end of        the cylindrical enteral prosthesis and extending over a length        L3 at least twice the length of the anchor element 2.

The prosthesis 2 is a known device called a stent made in particularfrom nitinol, the physical properties of which are known to the personskilled in the art. Stents are small tubes having controlled radialexpansion properties as a function of temperature. To be more precise,they undergo progressive radial expansion if their temperature risesabove approximately 20° C. This element is produced in the form of aspiral nitinol wire mesh entirely coated with one or more layers ofsilicone.

FIG. 2 represents a preferred variant of the anchor element or stent 2in which said main portion 2 a of said first wall extends from theupstream longitudinal end 2 ₁ of said first wall as far as anappropriately shaped downstream end portion 2 b of smaller diameter thanthe cylindrical main portion. The diameter D1 of the cylindrical mainportion at its maximum radial expansion is approximately 32 mm. Theoutside diameter D2 of the downstream end 2 ₂ of the first wall at itsmaximum radial expansion is approximately 24 mm. The length L1 of thecylindrical main portion is approximately 70 mm. The length L2 of theappropriately shaped end portion 2 b of the first wall is approximately20 mm. The diameter of said end portion 2 b decreases progressivelybetween the downstream end 2 ₂ of said main portion 2 a and saiddownstream end 2 ₂ of said first wall.

To be more precise, the diameter of the appropriately shaped downstreamend portion 2 b is reduced by surrounding it with an elastomer materialring 3 ₁ that has a diameter less than said diameter of said mainportion at its maximum radial expansion.

In the retracted configuration, this prosthesis 2 may adopt a diameterin the range 3 mm to 8 mm.

The sheath 3 and the elastic ring 3 ₁ are made from a biocompatibleelastomer material based on silicone or polyurethane.

In an embodiment represented in FIG. 2, the upstream end of the sheathcovers the anchor element 2 over the whole of its length, which latterelement is embedded in the elastomer constituting the sheath, whichmakes it possible to coat all the external surface of said anchorelement 2 as well as providing the connection between the sheath and theanchor element 2.

Said sheath when at rest has a length downstream of said anchor elementof at least 50 cm, preferably at least 1 m, a diameter D₂ in the range26 mm to 33 mm, and a wall thickness in the range 0.1 mm to 0.5 mm.

This distance of at least 50 cm, preferably 1 m, makes it possible toenvisage an implantation site 7 for the anchor element 2 at a distanceupstream of the anastomosis 5 of at least 50 cm, or at leastapproximately 1 m, as the case may be.

The sheath 3 is produced from a mixture of different types of silicone(LSR, RTV, and gel), as described above.

The surgeon produces the anastomosis by the usual method, oftenemploying a stapler. Once the anastomosis has been produced, theassistant inserts the introducer sheath.

FIG. 3 represents the various portions of the intestine, namely therectum 11, the anal passage 10, the descending colon 12, the transversecolon 13, the ascending colon 14, the small intestine 15, the stomach16, and the esophagus 17.

There are represented the two ends 6 a and 6 b of the resected intestinesegment and the join 5 between these two ends constituting theanastomosis.

FIG. 4 shows the insertion of the device of the invention, which isinserted in a retracted configuration 2A via an introducer sheath 4 thatconsists of a deformable semi-rigid plastics material tube with adiameter in the range 3 mm to 8 mm and a length in the range 70 cm to220 cm, into which the anchor element is inserted in retracted form,said sheath being positioned downstream of the anchor element inside theguide tube of the introducer sheath. Once the guide tube of theintroducer sheath has reached the implantation site 7, for example apoint approximately 1 m upstream of the anastomosis 5, the anchorelement may exit the end of the introducer sheath and adopt an expandedconfiguration 2B shown in FIG. 5. It should be noted that the time takento introduce the introducer sheath of the anchor element and to route itto the implantation site 7 is in practice less than the time after whichsaid anchor element expands radially because of the increase intemperature to which it is exposed inside the body.

FIG. 6 represents the complete device with the sheath 3 deployed afterwithdrawing the introducer sheath 4. The sheath 3 extends from theimplantation site 7 as far as the anal orifice 10.

Initially closed and housed inside the introducer sheath, the stent hasa very small diameter, notably in the range 3 mm to 8 mm. It passesthrough the anastomosis 5 and then enters the upstream intestine 12. Thesurgeon assesses the progress of the introducer sheath 4 and its correctplacement by palpating the introducer sheath via the intestinal wall andvisualizing the stent during its expansion. Once released into the lumenof the intestine, the stent progressively resumes its final diameter. Itmay be temporarily held in place by the hand of the surgeon clamping thestent via the walls of the intestine. The introducer sheath is thenwithdrawn. The sheath 3 unfolds spontaneously and progressively onwithdrawal of the introducer sheath 4. This passes back through theanastomosis and then the anal orifice 10 in the rectrograde direction,totally releasing the sheath 3. After an average delay in the range fourto six days, and because of the effect of intestinal contractions, thestent-sleeve assembly migrates progressively toward the anal orifice 10from the upstream anchor site, which is sufficiently upstream of theanastomosis, preferably at least one meter from it in terms of intestinelength, for the stent to reach the anal orifice five or six days laterand only after resumption of intestinal transit, after which the deviceis eliminated with fecal matter, as represented in FIGS. 7A and 7B.

FIG. 8 represents an introducer sheath 4 including:

-   -   a straight tubular external envelope 4 ₁ made from a semi-rigid        material so that it may be curved to follow the contours of the        intestine when the introducer sheath is routed into the        intestine from the anal orifice; the external envelope has an        outside diameter that is 20 mm to 40 mm less than that of the        wall of the intestine at the level of the anastomosis and an        inside diameter and a length able to contain said anchor element        2 when compressed in the retracted configuration and said sheath        deployed behind the anchor element, i.e. in practice a length in        the range 100 mm to 150 mm;    -   a buffer tube 4 ₄ disposed axially inside said envelope and the        distal end of which includes an abutment 4 ₅ that abuts against        said anchor element, which is itself immobilized by radial        expansion at the distal end of the external envelope 4 ₁; the        buffer tube has a diameter slightly less than the inside        diameter of the external envelope so as to contain the sheath 3        fixed to the downstream end of the anchor element, said sheath        surrounding said buffer tube 4 ₁; on withdrawal of the external        envelope, the buffer tube retains the anchor element and        therefore prevents withdrawal of the anchor element with the        envelope and forces the anchor element out so as to be deployed        radially against the wall of the intestine;    -   a flexible guide wire 4 ₂ inserted on the axis of the buffer        tube and the axis of said anchor element contained by the        external envelope in the retracted configuration; the distal end        of the guide wire is J-shaped to prevent trauma when it is        inserted; it may be made of metal or synthetic material;    -   an atraumatic cone 4 ₃ perforated axially to allow the guide        wire 4 ₂ to pass through it; the cone 4 ₃ has a diameter that is        greater than the inside diameter of the external envelope and is        disposed downstream of the external envelope to facilitate        routing the introducer sheath into the intestine.        The prosthesis is placed in the following manner:

1) The guide wire is inserted into the intestine as far as the anchorsite of the anchor element.

2) The proximal end of the prosthesis is inserted externally of the analorifice into the perforation of the atraumatic cone and then into theaxial channel of the anchor element and then of the buffer tube on theaxis of the introducer sheath.

3) The distal end of the external envelope of the introducer sheath ispushed along the guide wire inside the intestine, which pushes theatraumatic cone as far as the anchor site on the upstream side of theanastomosis.

4) The guide wire 4 ₂ is withdrawn.

5) The external envelope 4 ₁ is partially withdrawn, with the buffertube 4 ₄ held so that said anchor element is released.

6) The external envelope is withdrawn completely, together with thebuffer tube and the atraumatic cone 4 ₃.

According to the present invention, the device is used on an anastomosisas a preventive measure when there is no fistula. Nevertheless, theplacement of the device 1 with the introducer sheath 4 includesmaneuvers during its insertion that represent a potential hazard for theanastomosis in that they could injure it. A semi-rigid tube 8 called aprotector tube is advantageously used to prevent this hazard.

The protector tube 8 temporarily protects the anastomosis duringplacement of the device, i.e. during insertion of the introducer sheath4. The protector tube 8 is thus placed even before the introducer sheath4 is placed and manipulated. Once the anastomosis has been produced, theprotector tube is the first to be inserted.

This protector tube 8 is stiffer than the introducer sheath 4 andprotects the intestinal wall so that the introducer sheath 4 does notdeform the intestinal wall during its insertion.

The curved shape of the protector tube 8 enables it to espouse thecurves of the intestine. The tube has a curved central part 8 a similarto the curvature of the vertebral column at its lower end, which isreferred to by the person skilled in the art as the sacral concavitycurvature. Curvatures of this type are encountered in stapler devices.This tube 8 is open at both ends. The proximal end 8 ₄ of the protectortube 8 is flared, enabling it to espouse the anatomical shape of theanal margin outside the external anal orifice. The same end includes onits external face a slightly inclined straight rod 8 ₅ that is used tograsp the tube. The distal end of the tube 8 is not flared in order tobe inserted into the anal orifice and then routed as far as a pointupstream of the anastomosis 5. To this end, this non-flared end of thetube 8 is preferably reversibly blocked by an atraumatic cone 8 ₂mounted on a rod 8 ₃ situated inside the lumen of the protector tube.This atraumatic cone 8 ₂ prevents injury to the intestine duringinsertion of the protector tube 8.

The protector tube 8 has a length corresponding at least to the distancebetween the anal orifice and the anastomosis, i.e. in practice at least5 cm to 25 cm, and an outside diameter less than or equal to that of theintestine at the level of the anastomosis, in practice the diameter ofthe stapler used to produce the anastomosis, i.e. in the range 10 mm to40 mm, preferably in the range 20 mm to 30 mm. Its inside diameter is atleast equal to that of the introducer sheath 4, to enable the introducersheath to pass through it.

In practice, there are three types of anastomosis: colo-colic (colon tocolon), colo-rectal (colon to rectum), and colo-anal (colon to analpassage). Depending on the type of anastomosis, the joining area betweenthe two intestine ends is at a greater or lesser distance from the analorifice (which on this occasion serves as a reference point).Accordingly, starting from the anal orifice and in the upstreamdirection, a colo-anal anastomosis is at a distance in the range 1 cm to3 cm from the anal orifice, a colo-rectal anastomosis is at a distancein the range 4 cm to 10 cm, and a colo-colic anastomosis is at adistance in the range 11 cm to 20 cm from the anal orifice. This is whythe length of the tube 8 is up to 25 cm, in order to be able to reach acolo-colic anastomosis, the type situated farthest from the analorifice. For anastomoses nearer the anal orifice, not all the length ofthe tube need be introduced. The exact positioning of the tube 8 isalways effected under the visual control of the operator.

Once the distal end of the protector tube has been routed to a point afew centimeters upstream of the anastomosis, the atraumatic cone isremoved to free up the lumen of the protector tube. The introducersheath 4 is then inserted into the lumen of the protector tube. Thesemi-rigid nature of the protector tube 8 protects the anastomosis 5from rubbing by the introducer sheath 4. The farther the introducersheath rises in the upstream intestine, the more it rubs on the walls ofthe intestine and the greater the pressure exerted by the operator onthe introducer sheath. The lumen of the digestive tract has anon-negligible coefficient of resistance by virtue of its internal wallsand even by virtue of the contractions of the intestine. This appliesequally to withdrawing the introducer sheath 4.

In practice, once the anastomosis has been produced, the tube 8 with itsatraumatic cone 8 ₂ is picked up by the rod 8 ₃ and the whole isintroduced into the intestine via the anal orifice. The protector tube 8is pushed through the anastomosis 5 into the upstream intestine 12. Thedistal end of the tube 8 is positioned at 8 and the rod 8 ₃ comes intocontact with the anal margin; they are held in place by the hand of theoperator. The atraumatic cone 8 ₂, the diameter of which is slightlyless than that of the tube 8, is withdrawn. The introducer sheath 4 isinserted through the flared orifice 8 ₄ of the protector tube 8 in orderto push it through the protector tube. The subsequent steps unfold asdescribed above in relation to the use of the introducer sheath 4. Allmaneuvers effected during manipulation of the introducer sheath 4 areeffected via the protector tube 8, which provides a protective barrierfor the anastomosis and prevents it being injured. After completewithdrawal of the introducer sheath 4 the protector tube is withdrawn inturn.

The appropriately shaped end 2 b of the stent 2 facilitates its progressin the intestinal lumen. Nevertheless, the anastomosis region oftenfeatures a stenosis at the level of the junction between the twointestine ends and thus has a diameter less than the intestine on eitherside. This is caused by healing of the anastomosis. This stenosis maypotentially impede the progress of the stent 2 through the anastomosis 5and in the extreme situation cause closing of the stent in this area.Migration of the stent may always be facilitated by maneuvers exertingtraction on the proximal part of the sheath 3, but this is sometimes notsufficient. Assistance may then be provided by a protector tube 8, whichfacilitates the passage of the stent or in the extreme situation enablesre-opening of the stent.

It is a semi-rigid cylindrical tube that has the same curvature as thesacral concavity and the intestine, like the protector tube 8 describedabove, but extending from the anal orifice as far as the upstream sideof the anastomosis 5. One of its ends, referred to as the proximal end,is flared to adapt to the conformation of the anal margin. However, itsinside diameter is greater than that of the anchor element or stent atleast in the radially retracted configuration. Its length is identicalto that of the protector tube for placing the introducer sheath 4.

The maneuver entails identifying the anastomosis area under radioscopiccontrol. This area is easily found by virtue of the presence of theclips that were used to effect the anastomosis and the presence of thestent, which carries radio-opaque markings.

When the downstream end of the sheath arrives downstream of theanastomosis 5, the downstream end of the sheath 3 is inserted into thelumen of the tube 8 via its distal end. The sheath is brought out viathe proximal end of the protector tube. The protector tube 8 slidesprogressively along the sheath 3, which serves as a guide wire for it.It enters the anal passage and then the intestine. The operator pushesit into contact with the downstream end of the stent, where it isimmobilized. The downstream end of the sheath is pulled progressively.The upstream end of the sheath attached to the stent enters the lumen ofthe distal end of the tube. Traction continues to be applied to thedownstream end of the sheath. The downstream end of the stent followsthe upstream end of the sheath. The retraction properties of the stentenable it to adopt the inside diameter of the tube and to enter thelumen at the distal end of the tube, the diameter of which is at leastequal to that of the introducer sheath. Continuous traction on thedownstream sheath enables the stent to enter the tube 8 entirely. Thewhole of the tube 8 containing the stent and the sheath is thenwithdrawn via the anal passage.

FIG. 11 represents a preferred version of a device of the invention inwhich the sheath 3 covers the stent 2 only partly, covering all itsconical downstream end, the connection between the sheath 3 and thestent 2 beginning upstream of the conical end over an area 2 c that hasa length in the range approximately 3 mm to 30 mm, preferably in therange 5 mm to 15 mm, upstream of the upstream end of the appropriatelyshaped area 2 b.

The stent 2, which is made in the form of a spiral wire mesh, has asilicone coating 24 that is thinner than said sheath and confers on saidstent greater radial and longitudinal deformability than said sheath.Thus if the stent is immobilized upstream of the anastomosis, preventingit from deploying and/or migrating through the anastomosis, manualtraction may be exerted on the proximal end of said sheath, deforming itby reducing its diameter and stretching the rest of the stent tofacilitate its passage through the anastomosis.

The stent 2 preferably has at each end a thread-like extension known asa lasso approximately 10 mm long, preferably made from the same materialas the stent. As known in the art, traction on the lasso at thedownstream end of the stent then makes it possible to facilitatereducing the diameter of the stent and stretching the stent axiallyusing a commercially available instrument of the colonoscope orrectoscope type.

In contrast, and again in known manner, traction on the lasso at theupstream end of the stent makes it possible, in the event of jamming ofthe stent, to turn the stent inside out by pulling its upstream end 2 ₁inside itself in the upstream to downstream direction so as to free itfrom the intestinal wall, in which it may have become incorporated.

In known manner, the thread-like end 2 ₃ of the stent, called the lasso,extends from the periphery of the downstream end 2 ₂ or the upstream end2 ₁ of said stent.

In another embodiment, as well as or instead of the thread-likedownstream end called the lasso described above, a flexible strand withthe same characteristics as the lasso is attached to the proximal(downstream) end of the stent, around its periphery, and threadedthrough the mesh. Thus traction on this strand leads to almost completeclosure of the proximal downstream end of the stent at which the sheathbegins. This strand extends inside said sheath as far as its proximalend situated at the anus, so that access to said strand does notnecessarily require the use of a colonoscope or rectoscope. In the eventof incorporation of the stent, closing the proximal end of the stent bypulling on the strand helps to facilitate passage of the stent throughthe anastomosis.

The invention claimed is:
 1. A surgical device for temporary protectionof an anastomosis in the colon, the rectum, or the anal passage, thedevice including: a) a semi-rigid hollow longitudinal temporary anchorelement, a first wall of which defines a surface of revolution about alongitudinal axis, including a substantially cylindrical main portionwith a substantially circular section, and said first wall having anoutside diameter that may be varied in a controlled manner between: areduced outside diameter of, at most, 10 mm in a radially retractedconfiguration of said first wall; and a maximum outside diameter in amaximum radial expansion configuration of the cylindrical main portionof said first wall in the range 20 mm to 40 mm; said maximum outsidediameter of the anchor element being higher or equal to that of saidwall intestine in the colon, at rest, in the absence of intestinaltransit, and lower than the dilated maximum diameter of the wallintestine in the colon upon resumption of the intestinal transit so thatsaid anchor element is capable of remaining temporarily fixed to thewall intestine in the colon for at least three days in the absence ofintestinal transit by the only virtue of a radial expansion force of theanchor element against the intestinal wall, said anchor element notcomprising other fixing means than said radial expansion force capableof fixing the anchor element to the wall intestine, and the anchorelement is capable of being released and migrate by sliding in contactwith the wall intestine upon resumption of the intestinal transit; andb) a sheath having a flexible tubular wall permanently fixed againstsaid first wall of said anchor element; wherein: 1) said first wall ofsaid temporary anchor element includes said cylindrical main portion ofsaid first wall having a length of at least 50 mm; and 2) said sheathhas, when at rest, a length downstream of said anchor element of atleast 50 cm, and an outside diameter in the range 20 mm to 40 mm, and ismade from a biocompatible elastomer material having a wall thickness inthe range 0.05 mm to 1 mm; wherein the length of the sheath is such thatthe anchor element is able to migrate for at least three days from ananchor site of the anchor element in the colon on resumption of transitwhile the sheath covers the anastomosis.
 2. A device according to claim1, wherein said cylindrical main portion of said first wall extends froman upstream longitudinal end of said first wall as far as anappropriately shaped downstream end portion having a smaller diameterthan the cylindrical main portion, the outside diameter of thedownstream end of said first wall in the maximum radial expansionconfiguration being in the range 20 mm to 35 mm, and the length of saidappropriately shaped downstream end portion of the first wall being inthe range 10 mm to 30 mm, the diameter of said downstream end portiondecreasing progressively between said main portion and said downstreamend of said first wall, to facilitate the migration of the anchorelement through a stenosis of the anastomosis area of reduced diameter.3. A device according to claim 2, wherein the diameter of saidappropriately shaped downstream end portion is reduced by surrounding itwith an elastomer material ring having a diameter less than saiddiameter of said main portion in said maximum radial expansionconfiguration.
 4. A device according to claim 2, wherein a connectionbetween said sheath and said anchor element is produced by virtue ofsaid sheath covering at least an external surface of said downstream endportion of said anchor element.
 5. A device according to claim 4,wherein said anchor element is a stent-type enteral prosthesis coveredwith a coating of silicone or polyurethane type elastomer syntheticmaterial, said coating being more flexible than the elastomer materialof said sheath, and the connection between said sheath and said anchorelement being produced by virtue of said sheath covering said anchorelement over only part of the length of said anchor element including atleast said appropriately shaped downstream end of progressively reducingdiameter.
 6. A device according to claim 1, wherein: said anchor elementis made from a material conferring on it radial elasticity propertiessuch that it may be compressed radially in said retracted configurationand adopt said maximum radial expansion configuration after the radialcompression is released; and said biocompatible elastomer of said sheathis an elastomer-based biocompatible polymer material of silicone orpolyurethane type having said wall thickness in the range 0.1 mm to 0.5mm and having radial and longitudinal elasticity properties, shapememory properties, and non-stick properties.
 7. A device according toclaim 6, wherein said temporary anchor element is a stent-type enteralprosthesis said first wall of which is formed by a spiral elastomer ormetal wire mesh.
 8. A device according to claim 1, wherein said sheathis made from said elastomer-based biocompatible polymer material havingthe following properties: a Shore A hardness in the range 5 to 95; adegree of remanent deformation on compression (RDC) in the range 10% to35%; and a coefficient of friction in the range 0.30 to 0.90; andwherein said sheath presents radical and longitudinal elasticityproperties similar to, or greater than, those of the wall of the colon,and presents shape memory properties enabling the sheath to returnnaturally to an original shape of the sheath after the sheath isdeformed by bending.
 9. An insulation assembly of a device according toclaim 1, further comprising an introducer sheath including: a tubularexternal envelope that is adapted to contain said anchor element whencompressed in said retracted configuration, and to retain said anchorelement inside the distal end of said external envelope, and issufficiently long to contain said sheath, said external envelope havinga length of at least 110 cm; and means for routing the distal end ofsaid introducer sheath from an anal orifice to said anchor site in anintestine upstream of the anastomosis.
 10. An insulation assemblyaccording to claim 9, further comprising a protector tube that includesa portion of curved shape conforming to the curvature of a sacralconcavity, is stiffer than said tubular external envelope of theintroducer sheath, has an outside diameter and length such that saidprotector tube may be introduced via the anal orifice and extend betweenthe anal orifice and a point upstream of said anastomosis, and has aninside diameter and a curvature conforming to the curvature of thesacral concavity such that said protector tube is able to contain saidintroducer sheath and route it between the anal orifice and saidanastomosis.
 11. An insulation assembly according to claim 9, furthercomprising a means for disengaging said anchor element from the externalenvelope in the form of a buffer tube including an abutment at itsdistal end in contact with the longitudinal end of said anchor element,said sheath downstream of the anchor element surrounding said buffertube inside said external envelope.